Forget fuel, you can always order what you want , it is not a problem. 5-10 % is readily available everywhere.
If you consign it to sea shipping or a shipping agent make the crate heavy as you like but it will cost.
Do you want me to help you pack a model in a crate?
All my experience is making something for outsize , accompanied, luggage allowance. Airlines are used to Bicycles, windsurfs,etc.
Stuff your clothes in a cabin bag.
We always used British Airways, Every time we used another airline something went wrong. I did it 12 times to USA.
USA based airlines are the worst and can't be trusted to do what they say.
I think if it involves a internal flight using smaller aircraft =trouble.
BA will honour what they say. But try to establish a contact in customer service.
However getting a 15 kg model into a 32 kg box is not easy but can be done.
First if you have a freind/wife/travelling with you, you can both have the same allowance.
Wings and tail go in one box. Fuselage in the other.
Plenty of extra supporters buying tickets helps oil the wheels. Promise them a big thank you.
Pack it in loads of bubble wrap so it cant move.
The only strong point to fix it to the crate is the U/C. Strap the wheels down with lots of rubber bands.
Poke the crankshaft through a internal false former with a large hole. Not tight.
Fix a cut down propeller to the engine and fix with more rubber bands.
If you fix it rigidly, when, not if, they drop the box it will break the firewall etc.
My most successfully crate is made from 1/4 light ply.
The corners and all the seems are reinforced with short balsa triangles fixed with Gorilla glue.
You can run glass fibre tape all round the external joints.
If the box exceeded weight limit drill it full of holes with a hole saw. (makes hand grips anyway)
Put some rails on the bottom in case they want to fork lift it.
Make the lid secure but removable without tools. (over centre catches) for customs.
This was packing my PT22 for a trip to Top Gun and Jo Nall in 2014
Host of the European Scale Masters
6-10 September 2023